Preheat the oven to 350°F. Line 18 standard muffin tins with cupcake liners.

In the bowl of an electric mixer, combine the cake mix, water, oil, and egg yolks. Beat on medium speed for 2 minutes, scraping down the sides and bottom of the bowl once. (Alternatively, you can whisk by hand until fully combined.)

Divide the batter evenly among the prepared muffin tins, filling almost to the top. Bake for 15 minutes or until a toothpick inserted into the center comes out clean. Let cool completely.

Bring a couple inches of water to a simmer in a pan large enough to hold the mixing bowl.

In the bowl of an electric mixer fitted with the whisk attachment, combine the egg whites, sugar, white vinegar, and salt. Place the mixing bowl over the pan of simmering water, being careful not to let the bottom of the bowl touch the water. Heat the mixture, whisking constantly, until warm and the sugar has dissolved, about 3 minutes.

Remove the bowl from the heat and transfer to the mixer. Beat on high speed until stiff, glossy peaks form, 7-9 minutes. Add the vanilla and beat for another 30 seconds. Spread or pipe on cupcakes.

Place the oven rack in the middle of the oven and turn the broiler on high. Place the cupcakes on a sheet pan and put under the broiler to toast the frosting. Watch carefully. It will take about 2-3 minutes to get the frosting golden brown.

Put the graham crackers in a plastic food storage bag and crush with a rolling pin until you have fine crumbs with a few larger pieces. Sprinkle over the cupcakes.